1. Field of the Invention
This invention relates to methods, systems, and apparatus for the production of hydrocarbons from a subterranean formation.
2. Description of Related Art
Heavy oil from tar sand and bitumen deposits comprise significant resources for hydrocarbons to the extent that they can be economically produced. Typically, such heavy oil is heated to reduce the oil or mineral viscosity before it will flow, or to enhance flow. The predominant method for heating heavy oil is the injection of a hot fluid from the surface. One common industry practice typically referred to as “steam flooding” is carried out by injecting steam through a designated injection well in order to heat the surrounding hydrocarbons, which are produced simultaneously from one or more nearby production wells. An alternate commercial practice typically referred to as “cyclic steam stimulation” is carried out by intermittently injecting steam into a production well.
During the last decade, the steam-assisted gravity drainage (SAGD) method for recovering heavy oil has been extensively developed and is now the most common technique utilized for heavy oil production in Canada. The process utilizes twin horizontal wells drilled and extended into the base of a reservoir with the horizontal steam injector placed directly above the horizontal production well. In an ideal SAGD process, a growing steam chamber forms around the horizontal injector, and steam flows continuously to the perimeter of the chamber, where it condenses and heats the surrounding oil. As the viscosity of the oil decreases, it drains to the horizontal production well underneath. Thus, the use of gravity increases the efficiency of oil production.
Such thermal stimulation methodologies are limited in their effectiveness and efficiency in many operating environments.